Sound absorbing unit



SA C. APPEL March 28, 1939.

SOUND ABSORBING UNIT Filed Jan. 8, 1938 Patented Mar. 28, 1.939

UNITED STATES PATENT OFFICE 8 Claims.

This invention relates to apparatus for the absorption of sound and particularly to units for preventing the transmission of sound through conduits or ducts used for moving air to or from 5 speciiied areas in buildings.

In the construction of modern buildings it is customary to make provision for a system of sheet metal ducts for the introduction of conditioned air into the various rooms and for the l removal of stale air therefrom. In the air conditioning installations used in conjunction with such ducts, fans, humidiers and other machinery are used which are necessarily productive of noise. Street noises may also be carried in l through the ducts. In hospitals, schools and many offices it is very desirable or necessary to provide sound absorbing means to reduce or eliminate sounds which would otherwise be conveyed or possibly magnified by these sheet metal 20 ducts, and in theatres, concert halls and broadcasting studios the conditions in these respects are still more exacting.

The attempt has been made heretofore to solve the problem by inserting in air ducts tubes 25 oi' sound absorbent material bound in metal jackets. However, it has been found that the metal jackets are apt to chatter, it is impossible to ship the tube unit in assembled condition, and the cost of manufacture is relatively great, particularly the cost of assembling on the job with high cost labor. Furthermore, it is often necessary to make the unit oversize in order to insert the tubes and to waste space in the duct by using packing or lling material about the tubes.

In one aspect the present invention consists in a unit or section which may be inserted in any air duct and which comprises a self-contained frame supporting or combining a plurality of longitudinally extending cells made up of removable or interchangeable blocks or slabs of sound-absorbing material, such for example, as asbestos composition. As herein shown the frame may be made' up of angle and channel iron 45 members arranged to receive standard blocks of felted rock Wool in edgewise relation. 'I'his construction offers the important advantage of lightness, exibility in respect to size and convenience in erecting and repair. It is also advan- 50 tageous from the standpoint of cost in that each intermediate wall is common to two adjacent cells thus twice utilizing the sound-absorbing eect of each block or slab entering into the structure of the unit.

55 Units may be shipped assembled and ready for boltlng into the air ducts already in place or in process of construction. The operations of constructing the units are simple and require little skill because of a novel locking construction and the assembled units are designed to be rigidly 5 and conveniently secured in the ducts. Since the assembled units are self-contained and may be rigidly interconnected', there is no danger of vibration or rattling.

Tests have shown that a two-cell four-foot unit constructed according to the invention will cause a reduction of 42% in intensity of sounds transmitted therethrough. By measurement and calculation it is possible to estimate accurately the length of the cells required for any desired result. Such estimates, of course, vary according to the conditions surrounding each installation.

These and other features of the invention will be best understood and appreciated from the following description of a preferred embodiment thereof, selected for purposes of illustration and shown in the accompanying drawing, in which- Fig. 1 is a view in perspective of a typical nine cell unit constructed according to the invention,

Fig, 2 is a view in cross section along the line 2 2 of Fig. 1,

Fig. 3 is an end elevation showing the details of a joint, and Fig. 4 is a detail view of a spacing member.

Although a nine cell unit is illustrated in Fig.

1, it is to be understood that the principles of its construction are applicable to units containing any desired number of cells, 'I'he unit is rectangular in shape and comprises a metal frame sheathed with sheet metal, blocks or sheets of sound absorbent material cemented to the inside of the metal sheathing, and interior horizontal and vertical walls forming cells of sound absorbent material. 40

At each end of the unit is an outer or attaching frame comprising, at the front, four angle irons III, II, I 2 and I3 bolted'together to form an outwardly extending peripheral flange provided with bolt holes I5 which are used to attach the unit 45 in an air duct. At the rear of the unit is a precisely similar arrangement including four angle irons I6, I'I, I8 and I9. At each end of the unit is an inner frame disposed within and bolted to the outer frame. At the front, four angle irons 20, 2|, 22 and 23 are-bolted together to form an inwardly extending flange, an arrangement duplicated at the rear of the unit. 'I'he area Within the front frame is divided into nine equal parts by the provision of vertical angle irons 2l 55 and 25 and horizontal angle irons 2l and 21, the latter irons being notched to ilt over the backs of the vertical irons 2l and 25. strap irons I2 and 5l and similar horizontal irons u and Il divide the area within the rear frame into nine equal parts. Four channel bars 2l, I1, Il and 35 of U-shaped cross section are connected between the iront and rear frames, having their ends disposed adjacent to the ends of the horilontal iros 25, 21, Il and 25. The entire unit, with the exception o! the ends, is sheathed with metal. Il.

In Pig. 3 the Junction of the vertical angle iron 2l and the horinontal iron 21 is illustrated. A U-shaped spacing member 4I is bolted to the joint by a bolt Il, and, as will be seen in Fig. 2, a similar member 42 is bolted to the Junction o! the irons I2 and l5 at the rear of the unit by a bolt u. Boltedto the spacers Il and l2 are horizontal channel irons ll and It, held in back to back relationship by bolts Il and Il passing through the channel irons l5 and 46 and the spacers Il and I2. Referring now to Fig; 2, it will be seen that a block- 52 ot sound absorbing material isheld in horizontal position in the unit, its margins being confined in the channel irons 3l and l5, into which it may be slipped edgewise.

Between the backs oi' the channel irons l5 and l5 is disposed a similar block 5i, notched to fit over the spacers Il and I2 and supported in vertical position by the channel irons 45 and I5. Similar blocks l5 of sound absorbent material are cemented to the inner surface of the metal sheathing II, grooves being left in the bottom to receive the lower edges o1' the vertical blocks 5i.

Thus nine cells are formed having walls of sound absorbing material, and each cell has at least two walls in common with other cells. In assembling a unit the irons 2|, 25, 26 and 21 and the spacers Ii are not put in place until after the interior walls oi soimd absorbing material are lllt in.

It will be noted that the angle irons 2l, 25, 26 and 21 are secured in place so that they present V-shaped contour to the oncoming current of air and thus streamline the entering ends of the cells and minimize frictional losses. These irons serve as a binding to retain the constituent blocks in place in the unit. 'I'hey may be conveniently removed for purposes of replacement or repair permitting any desired block or slab to be moved endwise out of the frame.

I have referred to felted rock wool as one suitable material for the blocks.` Besides its sound absorbing characteristics it is light. flreproof and suillciently tough to withstand handling and use. It will be understood, however, that the invention is in no sense limited to this material and that other standard blocks or slabs of asbestos or magnesia composition may be employed with good advantage. Sheet cork or cork composition is desirableirom standpoints and may be used in special installations where iireproofing is not essential.

Having thus described my invention, what I claim asnew and desire to secure by Letters Patent of the United States is:

1. A sound absorbing unit which comprises front and rear trames formed of angle irons, a

Flat vertical` plurality of channel irons interconnecting said frames, a sheathing disposed around said frames, sound absorbing walls secured to the inner sur- `face oi' said sheathing and enclosing a murality oi' cells formed by vertical and horizontal walls of sound absorbing material supported by said channel irons, each cell having at least two walls in common with other cells.

2. A sound-absorbing unit having frames of angle irons at each end provided with attaching ilanges for supporting the unit, a plurality of horizontal channel irons interconnecting said frames, metal sheathing enclosing said frames and forming an open-ended rectangle, walls of sound absorbing material secured to the inner surface of said sheathing, and inner horizontal and vertical walls oi' sound absorbing material enclosed thereby and supported by said channel irons and disposed to form a plurality of cells.

3. In a sound absorbing unit comprising frame members and cells having walls of sound absorbing material, a plurality of pairs of horizontally disposed channel irons placed back to back, spacers secured to said frame members and disposed between each pair of channel irons, the inner horizontal walls of sound absorbing material in said cells being supported in the channels oi said channel irons, and vertical walls of said cells being supported between the spaced channel irons.

4. A sound absorbing unit comprising a frame 'f at each end including angle irons bolted together to form outwardly extending attaching flanges, inner frames secured to the said angle irons, upright and transverse supports secured to the inner frames, horizontally disposed members interconnecting corresponding corners of vvsaid inner frames, a plurality of horizontally disposed channel irons, and wallsY oi' sound absorbent V'blocks iitted edgewise into said channel irons and providing a multiplicity of cells within the unit having their intermediate walls in common.

5. A sound-absorbing unit having a metallic frame presenting oppositely arranged longitudinal channels, and blocks oi' sound-absorbing material fitted edgewse in the channels and providing in the unit a plurality of cells having common intermediate walls.

6. A sound-absorbing unit having a metallic frame presenting oppositely arranged horizontal and vertical channels, blocks of sound-absorbing material fitted in said channels to provide a multiplicity of cells, and V-shaped binding members acting to streamline the entering ends of the cells.

7. A sound-absorbing unit having a metallic frame comprising vertical members carrying U- shaped spacers and horizontal channel members connected to the spacers, and sound absorbing blocks fitted in said" channel members.

8. A sound-absorbing unit for use in air ducts,` comprising a rigid skeleton frame presenting opposed channels aligned horizontally and vertical- 1y, and thin blocks of compressed rock wool inserted edgewise in said channels in the form of a plurality of elongated cells of substantially equal cross section, each intermediate block serving as part of the common wall of two adjacent cells..

SAUL CARL APPEL. 

